Column Bases

[JIMEY]

I am working on my first "limited ductility" moment frame right now. I have to say that I am not sure what loads you are suppose to use when designing the baseplate/anchorage at the base of the columns. The building is being designed to the "National Building Code of Canada" because it is in Canada, as well as all relevant Canadian codes.

The problem as I see it is that the steel code does not explicitly state how to design the base plate. I would imagine that it needs to be designed to at least the nominal or probable resistance of the frame, perhaps with an upper limit of some sort.

And then my other concern would be how to check the foundation for bearing/anchorage. What loads would you use for that. Do they need to be different because the ductility of the concrete is different than the ductility of the steel? If so, does that also apply to the anchor bolts, or not?

Theses are the sort of things that I would like to have answered. I realize that probably only a few people on these boards know the Canadian codes, but I don't think that matters because the principles should be the same everywhere.

Thank you very much in advance.

 

[msquared48]

Is there a Commentary on the NBC of Canada you could refer to?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[JIMEY]

There is a commentary to the steel code. It does not mention base plates.

 

[pwht1]

You've left quite a few variables out of your post, so it's little difficult to answer specifically.

1) Are the columns pin-based or moment?

2) Have you done a static analysis with wind, earthquake, snow loads etc to determine the column base reactions?

3) Not sure about Canada but in Australia each connection must have a minimum strength that is relative to the connecting member. For example, connections in rigid construction should be able to transfer a moment 0.5 times that of the design member. Surely the Canadian code has a section on connections???

4) Are the base-plates rigid, flexible or semi-flexible? Most base-plates that I've designed have been based on yield-line theory ie flexible, but it's a pain in the arse to do.

That will do for now, good luck.

Paul